Embodiments of the invention relates generally to cooling devices, and particularly to, cooling devices based on a magneto-caloric effect (MCE).
Cooling devices may be used for a variety of cooling systems, such as refrigeration, air conditioning, electronics cooling, automotives cooling and industrial temperature control. Typically, existing thermal transfer devices, such as those relying on vapor-cycle refrigeration cycles, are relatively inefficient and environmentally unfriendly due to mechanical components such as compressors and the use of refrigerants.
Magnetic refrigeration techniques based on the magneto-caloric effect may be used as an alternative to conventional vapor-cycle refrigeration. Typically, cooling devices based on the magneto-caloric effect include a magneto-caloric material that is subjected to a magnetic field. The magneto-caloric material functions as a refrigerant and starts in thermal equilibrium with an environment to be refrigerated and the environment where the extracted heat is dissipated. Near a transition temperature of the magneto-caloric material, adiabatic application of a magnetic field reduces the magnetic entropy significantly by ordering the magnetic moments. This results in an increase in the temperature of the magnetic material. The MCE is defined in terms of an adiabatic change in temperature or isothermal change in magnetic entropy. This phenomenon is reversible for most magneto-caloric materials. Thus, adiabatic removal of the field reverts the magnetic entropy back to its original state and cools the material accordingly.
In operation, the magneto-caloric material is coupled with a heat transfer fluid. On magnetization, the heat transfer fluid gains heat and transfers energy to a hot sink. Further, removal of the field reduces the temperature of the magneto-caloric material to a point lower than it was prior to magnetization. Thus, the material can cool a cold source coupled with the heat transfer fluid. During cold startup, a cooling device achieves a desired cold box temperature starting from an initial equilibrium temperature. Further, such devices are also required to tackle changes such as change in environment temperature, change in desired cold box temperature, change in cooling load etc. However, existing cooling devices based on the magneto-caloric effect take a long time to achieve the desired cold box temperature and are not scalable to tackle changes in the environmental temperature, desired cold box temperatures and cooling load changes.
Accordingly, it would be desirable to develop an efficient cooling device based on the magneto-caloric effect. Furthermore, it would be desirable to provide a cooling device that is able to achieve fast, efficient and robust cold start-up and is scalable to tackle changes in the environmental temperature, desired cold box temperatures and cooling load changes.